Discoveries
by Noma
Summary: Charlie's consulting job takes a turn for the worse when someone is killed. Now Don races against time to save his brother.
1. Data

Don liked spending time in his family home. No matter how long he had lived away from the house, it still felt like home, with its unique and familiar smells and sights. He was sitting in the living room with his father watching a ball game, but his brother was absent.

Don and Charlie had never been close growing up. The five year age difference as well as Charlie's extraordinary abilities had put a wedge between them that Don felt was only recently beginning to be broken down. He knew he wasn't completely past his issues with his brother and he also knew Charlie wasn't past some of his problems with him, either. Those issues were part of the reason he had tried to spend time at home with his family ever since his return to LA. He knew that even if his brother and he could never mend their relationship, at least they were giving their father the opportunity to spend time with both his boys. He never had much of that when they were growing up.

But Charlie was annoyingly absent.

"What's Charlie up to these days, dad?" Don asked, trying to sound casual and knowing his father saw right through it.

"He said something about Kalman's filter," Alan said.

Don's gaze left the TV and rested on his father, trying to figure out what the older man had just said.

Alan, sensing his son's confusion could only smile. "I have no idea what that means, but that's what he said."

Don glanced at his watch, noting the late hour. A math professor shouldn't be working at this time of the night; but his brother never had played by the rules everyone else seemed to live by. "He's working odd hours again?"

"Yeah. He mentioned something about being on a tight schedule," Alan replied, returning his focus to the game. He didn't mind his son's working habits as much as he sometimes pretended. Charlie enjoyed his work so much that he could sometimes get lost in it and Alan loved that passion. He just knew that sometimes Charlie needed to be brought back to reality or he'd starve to death.

He chuckled softly when he noticed Don checking his watch for the third time. Don never seemed to realize that the same tendencies that made him worry about Charlie, also made Charlie worry about him. They both got lost in their work and both Charlie and Alan were painfully aware that Don's job was a little more dangerous than being a professor of applied mathematics.

Don resigned to watching the ball game without his brother. It wouldn't be the first time Charlie had worked in the garage well into the morning.

1

Charlie looked at his garage wall, imagining what was happening in the house, beyond the barrier. He could hear the ball game on TV and knew his brother was probably wondering where he was. He only hoped Don would be able to understand that sometimes his work was important enough for him to be locked away in the garage, away from everyone.

He set an alarm clock to let him know when it was time to eat. He knew he would only hit the snooze button and he hoped that he would eventually get tired of playing with the alarm and go eat. He figured it worked every morning when his goal was getting up, so it should work where supper was concerned.

By the time the alarm went off for the fifth time, he knew he had to get up and go into the kitchen. He didn't really want his father or brother to come by and force him to eat. He especially didn't want them to know that he was locking his door while working in the garage. It was sensitive data he was working with and he couldn't afford to have someone walking in, even if they wouldn't understand a thing they saw. He knew that a locked door would lead to questions and his answers – or lack thereof – would lead to worry, by both his father and his brother.

His father worried too much as it was.

Charlie knew why his father worried. There was a time in the not so distant past when Alan feared he had lost both his sons. Don was in the Fugitive Recovery Squad, barely calling home and Charlie, far more detached from his father and brother, had allowed himself to sink into his world of numbers and equations. Their mother's illness had brought Don back to LA, and her death seemed to have reawakened Charlie to the world. But now he knew Alan was worried about losing them all over again, what with Don's continuously dangerous cases and Charlie's consulting work with his older brother.

Charlie walked out of the garage slowly; making sure that the door was locked behind him. Neither Don nor Alan reacted when he entered the house but he could sense their unvoiced comments. He knew they thought he worked too much, but what they couldn't seem to understand, without it being said, was that he wasn't working on just any school project. He was working on something important. There were times in his life he thought they would never understand him, that the distance between him and his brother would never be bridged. And there were times, however rare, when he looked at his brother and thought he actually got it; got him. But Don never seemed to understand what made him tick. He never seemed to understand why Charlie acted the way he did. And no matter how much Charlie tried, he could never seem to make him understand.

1 - 2

Lorelei Roberts shut her eyes tight, trying to stop the burning sensation. She knew her body was telling her she had been staring at the computer screen for way too long and that it was time to sleep, but Lorelei refused to give in to it. She had to get the results of the last run of the program to Charlie ASAP so he could give her something by morning. It hadn't taken long before she and Charlie had fallen into a familiar working rhythm with each other. She just wished he didn't have to be the gentleman all the time and insist on taking the graveyard shift. She had seen him a few days ago and it looked like he wasn't getting much sleep, night or day, and it now seemed to be catching up with him. She only wished it would all end soon. National Security was National Security, and Lorelei knew that she, Charlie and the others would do whatever it took to help the Air Force with this one, but the human body could only take so much, and Charlie was known for pushing the envelope.

The program finally finished running, and Lorelei opened the output file. She smiled as she saw the numbers her program had generated, and she printed the file. Putting it in a package, she called to the Staff Sergeant, who was standing quietly outside the office, waiting for the data he needed to deliver to Professor Eppes.

1 - 2 - 3

Don was startled awake by a knock on the front door. He had fallen asleep watching the game with his father, who had since gone upstairs and was now fast asleep in his own room. He got up slowly, stretching the muscles that had been abused by the not so comfortable sofa. Walking to open the door, he glanced at his watch. It was almost one o'clock in the morning.

Don thought someone coming to the house at that hour was strange enough, but he found the identity of the man even more surprising. He looked the new arrival up and down, from the clean cut haircut to the spotless Air Force uniform. The Sergeant looked nervous, like he was on some very important mission. What Don couldn't figure out was why someone from the Air Force would be knocking on the door of the Eppes house, and in the middle of the night, no less.

"Is this the residence of Professor Charles Eppes?" The young Staff Sergeant seemed a little too formal for this hour of the night.

"Yeah, but I'm pretty sure he's asleep. Who are you?" Actually, Don had a nagging suspicion that Charlie was still in the garage working, but it was none of this man's business.

"Staff Sergeant Michael Cruz, US Air Force. I need to speak with him, sir." Staff Sergeant Cruz hesitated for a second before deciding to continue, "This is urgent."

Don was wide awake by now and quite curious about the young man. Just as he was about to ask another question, Charlie entered the living room from the back of the house.

"Michael, I thought I saw your car, why are you up this late?" Charlie took one look at Don and realized Michael's visit would seem rather odd to his brother. He tried to give Don a brief smile to tell him he was sorry, but Don only seemed more perplexed.

"I wanted to get Lorelei's data to you before I clocked out. She seemed really optimistic about this one. God knows we've had enough planes in the sky to give you what you asked for." Michael spoke enthusiastically, handing Charlie the data. Nothing he had said was classified since anyone could see there were planes in the air, but Charlie really didn't feel comfortable with the idea of his family knowing how deep into the military this thing went. They had an annoying tendency of worrying too much.

"Go to sleep, then. I'll work on this and call Lorelei in the morning." Charlie hated working with the team over the phone, but he knew they all needed their space to get this work done. And between Lorelei's many computer screens and his neverending number of blackboards, they simply could not work in the same room.

"Good night, Charlie. Sir." Michael nodded at Don and left the house, leaving Don staring at Charlie and Charlie reading his data, doing his best to ignore Don's look.

Don let himself contemplate the idea he was dreaming this bizarre conversation for a second but then realized this was way too weird to be a dream. If someone had asked him what was the last thing he expected to find on his brother's doorstep at 1 am, a USAF Staff Sergeant would defiantly have made the short list.

"What the…" Don couldn't finish the sentence. "What was that?"

"Just a consulting job and before you ask, I really can't talk about it."

As Charlie turned to walk back to the garage, Don spoke up again. "You're going back to work?"

"I really need to finish this. I'll sleep when I'm done." Charlie knew his brother wouldn't be able to ask him to do otherwise. Don had often skipped nights of sleep when working on a case.

"And when will that be?"

Charlie gave his Don a knowing smile and went back to the garage. Some things were better left unanswered.

Don sighed lightly. If he were a betting man, he would bet Charlie would not get much sleep any time soon. He stalked up the stairs to his old room, thoughts of the comfortable bed pushing away the image of his brother's tired eyes.

1 – 2 – 3 - 5

**Please R&R**


	2. Bad news

Thank you for all the great reviews, guys.

The beta'ing process is taking forever, but I promise I'll update soon.

I know there's a lot of Don in these chapters but I promise more of Charlie soon.

1 – 2 – 3 - 5

Time seemed to have no meaning when working the night shift. There were no people around, no one to tell you it was time for a break or a meal. Data seemed to make more sense when the stars were out. When Charlie heard the birds outside his garage, he knew morning was just around the corner. For a while he just ignored it, but he knew some things couldn't be ignored forever. He got out of his chair, rubbing his tired eyes. He was planning on a good shower and a hot cup of coffee, thinking that he just might fool his brother into believing he'd gotten some sleep.

He was almost finished with this batch of data and he would be happy to make this morning phone call to Lorelei because they had made some significant progress with their work. Maybe after giving her the new algorithms, he would sleep for a few hours. His vision was getting blurry enough for him to consider it.

Everyone was awake by the time Charlie got out of the shower. Alan was cooking breakfast while Don was reading the morning paper. Charlie headed for his room to make his call. Breakfast, and Don's third degree, could wait until he was done.

Charlie was surprised when a man's voice answered in Lorelei's office.

"Hello, is Lorelei there?"

"Charlie?"

"Colonel Harrison?"

Thomas Harrison was in charge of the project both Charlie and Lorelei were consulting for. He wasn't supposed to be in Lorelei's civilian office.

"Charlie, you need to come in. Lorelei's been killed." Colonel Harrison spoke slowly.

Silence.

"Charlie?"

Charlie didn't know what to say. He and Lorelei had often worked together; she was the one that had recommended him for this job. Now, he wished he had never heard about it. They were friends and Charlie didn't have many friends that understood him. Lorelei, dead? That didn't seem to make any sense. He had seen her two days ago, when he had decided to drop off some data himself instead of using the AF Sergeants as his delivery guys. An image of her from two days ago surfaced in his mind, almost making him gasp.

"What? How?" Charlie's voice reflected his shock.

"I'm sending someone to pick you up. Are you calling from home?"

"Yeah." Charlie didn't trust himself with too many words.

"I need you to listen to me. Because Lorelei was a civilian computer expert and her office was on federal property, the military will not be investigating this. The FBI will. If you see them before we talk, I need you to say nothing until we make sure they have clearance, ok? Charlie?"

"Yeah. I'll see you later." Charlie hung up the phone, barely aware of his own actions as he sat on the bed behind him. He knew shock had a tendency to grab hold of him and send his mind to terrible places.

It had happened when his mother was sick.

It had happened when Don was shot.

He could feel it happening now. P vs NP seemed to give him comfort that he couldn't explain to anyone. Math was the only thing that could switch his thoughts to something else for a second or two, and he grabbed hold of those seconds like a lifeline. It was the only thing that kept him sane at times, the only thing that calmed him down. All the other seconds in the day were spent on trying to distract himself from whatever had caused the initial shock.

Charlie kept sitting on his bed, staring into space.

He didn't remember there was breakfast waiting downstairs.

He didn't remember he was hungry.

He didn't remember his family waiting downstairs for him to eat with them.

He kept staring, waging his own battle against P vs NP.

1 – 2 – 3 – 5 – 8

Don was just about to take his first bite of his breakfast when his cell phone rang. Phone calls in annoying times were an occupational hazard that Alan understood but still hated.

"Eppes." Don stepped away from the table.

"Don, we have a new case. A Dr. Lorelei Roberts was killed in her office. She provides some computer services to the LA Federal bank so we were asked to intervene. Her sister also said she had some big government consulting job on developing some kind of a new computer algorithm, so we think her work might be the reason she died." Don heard the slight hesitation in David's voice before he continued, "Maybe you should bring Charlie with you; her work might make sense to him."

"Right."

Don was already up the stairs to his brother's room when David gave him the address for Lorelei's office. He hung up the phone as he entered his younger brother's room.

"I need your help, Charlie." Don hated saying those words. He hated asking his little brother for help with his own job. Whenever those feelings crept up on him, he would tell himself the case was all that mattered. Finding the killer was the most important thing.

It had taken him a while to understand two things. One was that Charlie was gifted and that no one else that worked for the FBI could do the things he did. He always knew his brother was special, but he didn't quite understand it until he had seen its effects on his own work.

The second thing he had realized was that there was no cockiness in the way his brother agreed to help. There was no self importance or a feeling of superiority. His brother simply liked helping him with a job that mattered.

But he still hated asking him for help.

"Charlie?" It took Don a second to realize his brother was staring into space and didn't seem to hear a word he was saying.

"What?" Charlie seemed to stir back into the real world when his brother stopped right in his line of sight.

"Are you ok?"

"I'm a little busy these days, Don. Don't think I have time for something new." Charlie avoided answering Don's question simply because he didn't know the answer to it.

"Maybe you should get some sleep." Don eyed his brother carefully, trying to decide if this behavior was because of his lack of sleep, or if something else was going on.

"Yeah, maybe."

Charlie made no attempt to move.

"I'm going to go to work, and you are going to sleep. I'll come back if there's anything you can do."

No comment.

Don quietly exited the room, hoping his brother would indeed go to sleep. Charlie used to drift away like this on a regular basis when they were younger, but Don hadn't seen him staring into space quite like this in a while, and it didn't sit well with him.

1 – 2 – 3 – 5 – 8 – 13

**Please R&R**


	3. The Crime scene

My beta is back and I'm back on track.

Enjoy!

1 – 2 – 3 – 5 – 8 – 13

Don arrived at the scene thirty minutes after his conversation with Charlie, his concerns for his brother hidden in a corner of his mind that would be reawakened once his job was done.

He took in the scene around him as he stepped into the office of Dr. Lorelei Roberts. The room was tidy, with three computer screens at a working table to his right and an office desk in front of the door. On the floor laid the body of a short, redheaded woman he knew to be Lorelei Roberts. She was dressed casually, like someone who did not entertain many people in her office. People in Air Force uniforms sat in front of Lorelei's computers. It seemed like an odd coincidence that he was meeting AF men for the second time today, but Don tried not to dwell on it. His immediate reaction was to ask David why they were touching the evidence.

"Dr. Roberts has been working on classified data, and the Air Force doesn't want us to go over it until they make sure we have clearance," David explained.

"Ok, I can understand that, but don't let them touch it."

"Excuse me." An officer approached Don. "I'm Colonel Harrison, United States Air Force. I'm in charge of this project. And you are?"

Colonel Harrison was a tall, light haired man with striking blue eyes who was exuding authority from every pore in his body.

"I'm Agent Don Eppes, FBI." Neither Don nor David missed the surprised expression on Colonel Harrison's face. "What?"

"Eppes? As in Charles Eppes?"

"Yeah, he's my brother. How do you know him?" Don's every instinct told him he wasn't going to be happy with the answer.

Harrison didn't respond immediately. Instead he called over to a Staff Sergeant who was giving a statement to one of Don's men. This time it was Don's turn to be surprised as he saw the same man who had awakened him last night.

"Staff Sergeant Cruz," the Colonel barely looked at the Staff Sergeant who was also slightly surprised to see Don. "Is Lt. House back yet?"

"Probably, sir. She said she would try and keep Dr. Eppes away from Dr. Roberts' office, so she might be outside."

"Thank you, Staff Sergeant." The Colonel dismissed the young man and faced the FBI agents, "I know you probably have some questions. May I suggest we do it somewhere else?"

Don nodded and motioned for the Colonel and agent Sinclair to step outside. It was a beautiful day, albeit a bit chilly, and the three men enjoyed the light touch of the sun as they stepped outside the small building. The entrance to the building was closed to the public and was filled with a significant number of LAPD officers, AF officers and FBI agents. Don spotted his little brother the second he existed the building. Charlie was sitting on the curb; only a few feet to his left, obviously distraught. Behind him stood a well built, dark haired Lieutenant, completely alert to her surroundings. Don realized she was functioning as a bodyguard for his brother. The very notion of Charlie needing a bodyguard sent shivers down Don's spine.

Don stared at the Colonel as realization suddenly hit him. His brother hadn't been tired when he asked him for help earlier today; he had already known about this murder. Every instinct he had as an FBI agent told him to talk to the Colonel and get to the bottom of this, yet every instinct he had as Don, Charlie's big brother, told him to get to his brother as soon as possible. Thomas Harrison seemed to understand that right away.

"Dr. Roberts and Dr. Eppes worked together on a project for us along with a number of other people. We're assuming Dr. Roberts' death had something to do with her work, and we're protecting everyone who even touched this project. I will make sure you have clearance as soon as I can; then I'll give you access to the data you need. Until then, I hope you can work with what you have." Colonel Harrison sighed lightly and looked at Don, speaking in a quieter, gentler tone, "Maybe you should talk with him. I don't think he's doing too well."

Don didn't need to be told twice. He knew his brother's track record with death. He thanked the Colonel with a soft nod and walked over to where Charlie was, once again, staring into space.

"You okay, buddy?" Don sat next to Charlie on the sidewalk.

"No." It was nothing more than a whisper, but Don heard it.

"What are you thinking?"

Charlie closed his bloodshot eyes. Slowly, he looked up to his brother, wondering if he could ever understand. "Trying not to think about P vs. NP."

Don could see all the sorrow that went into saying that sentence, all the regret over what happened when their mother was sick. "I never understood that."

"I know." There was no disappointment in Charlie's reply, only acknowledgment of what they both knew to be true.

"You knew her well?" Charlie flinched slightly when Don used past tense.

"Not well, but we've known each other for a long time."

"I'm sorry, Charlie."

"I know." Again, only an acknowledgement.

"You were working on this project with her," Don half asked, half stated.

"Yeah."

"Charlie," Don paused, waiting for Charlie to look at him, "I need to know. Are you in danger?"

Charlie could see the fear and hesitation in his brother's eyes. He only wished he could tell him there was no danger. "I don't know. I don't know why anyone would... anyone would do this." He looked away from his big brother as his voice cracked, doing his best to compose himself.

"Alright. It's okay. We'll figure this out."

"It's not okay." Charlie seemed to have aged twenty years in the short second it took Don to finish his sentence. "It's not okay, because she was a computer programmer and I'm a mathematician and this kind of thing is not supposed to happen to people like us."

"Dr. Eppes," Colonel Harrison seemed to hesitate before continuing. "One of our controllers in NORAD got a note saying they'd stop us from improving Kalman's filter and prevent another catastrophe. It's a declaration of war and we need your help to fight it." Harrison knelt down to be at the same eye level with both of the Eppes men. "I know this is hard, but I need you to work with the other programmers and controllers and help us fix this." The Colonel used his best commanding voice to try and get a reaction from the younger Eppes.

Charlie looked down at the pebbles on the side of the road, refusing to look the Colonel in the eyes. "I can't help you anymore. I just can't focus on this right now. I'm sorry."

He sounded like he was about to crack. It reminded Don of the last time Charlie closed down and worked on P vs. NP. When Don confronted him regarding his work, Charlie sounded like a wounded animal. He had seen Charlie do this once or twice before and did not want to see him being pushed into something that was too much for him. He was getting scared for his brother's mental health.

Don put his hand on Charlie's shoulder, trying to convey his thoughts. "I don't think Charlie should be here right now," he looked pointedly at Harrison. "He should go home and get some sleep. Whatever this is, it can wait a day."

Colonel Harrison gave Don a short nod, "You should keep an agent on him."

As they all got up to leave, Don leaned close to Harrison and said quietly enough for it to stay private, "I know, Colonel."

Don was having a bad day, and he didn't like Harrison's attitude one bit.

"Agent Grant," Don called out to the young agent. Agent Grant walked over to his boss, his long legs carrying him quickly through the distance. "I want you to take Charlie home. He's going to go to sleep and spend the day in the house. We have reason to suspect he might be in danger, so keep your eyes open."

Charlie stood quietly next to Don. He never met Adam Grant before and didn't give him much notice now. His mind was in Lorelei's office. He couldn't help wondering how she was killed.

"Yes, sir." Agent Grant nodded to Don and walked to his car, giving the brothers a minute together.

"Get some sleep, Charlie. I'll get to the bottom of this and I'll see you soon."

Charlie simply nodded and walked away, barely looking at his brother. Nothing seemed to make sense anymore.

1 – 2 – 3 – 5 – 8 – 13 – 21

**Please R&R**


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